Digital three-dimensional manufacturing, also known as digital additive manufacturing, is a process of making a three-dimensional solid object of virtually any shape from a digital model. Three-dimensional printing is an additive process in which one or more printheads eject successive layers of material on a substrate to build objects of arbitrary shapes. Three-dimensional printing is distinguished from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling.
The production of a three-dimensional object with these printers can require hours or, for large objects, even days. One issue that arises in the production of three-dimensional objects with a three-dimensional printer is consistent functionality of the ejectors in the printheads that eject the drops of material that form the objects. During printing of an object, one or more ejectors can deteriorate and eject the material at an angle from an intended direction; eject drops that are smaller than an ejector should eject; or fail to eject any drop at all. An ejector suffering from any of these operational deficiencies is known as a malfunctioning ejector. If the operational status of one or more ejectors deteriorates during object printing, it is not typically detected during printing. After the printing is completed, the defect may or may not be detectable, though it may have compromised mechanical integrity, esthetics, or other important qualities of the printed object. Consequently, print jobs requiring many hours or multiple days can produce objects that do not conform to specifications due to malfunctioning ejectors in the printheads. Once such defects are detected, the printed objects may have to be scrapped, restorative procedures applied to the printheads to restore ejector functionality, and the print job repeated. An apparatus that enables detection of malfunctioning ejectors while printing would enable restorative procedures to be applied during object printing so that a properly formed object can be produced. In this manner, product yield for the printer is improved and the overall printing process is performed more efficiently. The apparatus should be able to detect malfunctioning ejectors that eject a variety of materials, such as clear, colored, translucent, phosphorescent, soft, hard, any of a variety of polymers, and wax-based materials.